The present invention relates to a disk storage system, a thin film magnetic head therefor and a fabrication method thereof.
The present invention relates to a magnetic core for a magnetic head, and more particularly to a recording head for a dual element head for a disk system having a high recording density.
In recent years, the recording density of a disk storage system has become higher and the magnetic coercive force of recording medium has increased; accordingly, there is a need for a thin film magnetic head which is capable of sufficiently recording on a recording medium having a high magnetic coercive force.
In order to realize this, it is necessary to use a material having a high saturation magnetic flux density (B.sub.S) as a core material of the magnetic head. In the past, a 80Ni-Fe alloy film of 3 .mu.m thickness has been used for the core material.
However, since the resistivity of the 80Ni-Fe alloy film is as low as 16 to 20 .mu..OMEGA..cndot.cm, the eddy current loss becomes large in the high frequency bands. Therefore, the strength of the recording magnetic field of the magnetic head in a high frequency band is decreased, and accordingly the recording frequency is limited to about 30 MHz at maximum.
As an alternative material, Co system amorphous materials and a Fe-Al-Si sendust alloy thin film are proposed. However, these materials are not in practical use as yet because the former is thermally unstable, since the material is amorphous, and the latter has a disadvantage in the fabrication process as the magnetic core material for the inductive head, since it requires a high temperature heat treatment at nearly 500.degree. C.
In recent years, three-element group materials of Co-Ni-Fe have been proposed (Japanese Patent Application Laid-Open No. Sho 60-82,638, Japanese Patent Application Laid-Open No. Sho 61-76,642, Japanese Patent Application Laid-Open No. Sho 64-8,605, Japanese Patent Application Laid-Open No. Hei 2-68,906, Japanese Patent Application Laid-Open No. Hei 2-290,995).
Although the saturation magnetic flux density (B.sub.S) of these three-element system materials is as high as 1.5 T, the resistivity is not large and the crystal grain size is not small in the 80Ni-Fe alloy; and, in addition to this, there is a disadvantage in the high frequency characteristic as in the 80Ni-Fe alloy.
On the other hand, the memory capacity of the disk storage system has been steadily growing year by year, and areal density of a 3.5-inch type disk in production now has been increased up to 350 MB/in.sup.2.
In this case, the data recording frequency is nearly 27 MHz, which is near the performance limit of a magnetic head using the 80Ni-Fe alloy film or the Co-Ni-Fe alloy film.
Although there is proposed in Japanese Patent Application Laid-Open No. 3-68,744 a magnetic film for high frequency use formed by adding Nb, Ta, Cr, Mo to (40-50) Ni-Fe through a sputtering method, it is difficult to magnetically form a thick film using a sputtering method because the material has a large magnetocrystalline anisotropy.